Advances in Brain Amyloid Imaging

A Peculiar Tau Accumulation Pattern Identified Via 18F-Florzolotau PET Imaging in a Patient With Frontotemporal Dementia Caused by a Mutation in the MAPT Gene

ABSTRACT

We reported imaging findings with a peculiar tau accumulation pattern in a 56 year-old woman with frontotemporal dementia caused by Q351R mutation in the microtubule-associated protein tau (MAPT) gene. She had a 10-year history of gradually worsening memory loss. 18F-FDG PET demonstrated hypometabolism in medial temporal lobes, but 18F-florbetapir PET manifested no abnormal amyloid beta deposition, which ruled out Alzheimer disease. 18F-florzolotau PET showed tau proteins accumulated in medial temporal lobes, basal ganglia brainstem, and cerebellum. The pattern is different from other known MAPT gene mutation. Multitracer imaging can help differentiate between Alzheimer disease and frontotemporal dementia caused by MAPT mutation.

Acceptable performance of blood biomarker tests of amyloid pathology - recommendations from the Global CEO Initiative on Alzheimer's Disease

Anti-amyloid treatments for early symptomatic Alzheimer disease have recently become clinically available in some countries, which has greatly increased the need for biomarker confirmation of amyloid pathology. Blood biomarker (BBM) tests for amyloid pathology are more acceptable, accessible and scalable than amyloid PET or cerebrospinal fluid (CSF) tests, but have highly variable levels of performance. The Global CEO Initiative on Alzheimer's Disease convened a BBM Workgroup to consider the minimum acceptable performance of BBM tests for clinical use. Amyloid PET status was identified as the reference standard. For use as a triaging test before subsequent confirmatory tests such as amyloid PET or CSF tests, the BBM Workgroup recommends that a BBM test has a sensitivity of ≥90% with a specificity of ≥85% in primary care and ≥75-85% in secondary care depending on the availability of follow-up testing. For use as a confirmatory test without follow-up tests, a BBM test should have performance equivalent to that of CSF tests - a sensitivity and specificity of ~90%. Importantly, the predictive values of all biomarker tests vary according to the pre-test probability of amyloid pathology and must be interpreted in the complete clinical context. Use of BBM tests that meet these performance standards could enable more people to receive an accurate and timely Alzheimer disease diagnosis and potentially benefit from new treatments.

Differential centiloid scale normalization techniques: comparison between hybrid PET/MRI and independently acquired MRI

OBJECTIVE

Centiloid (CL) scales play an important role in semiquantitative analyses of amyloid-β (Aβ) PET. CLs are derived from the standardized uptake value ratio (SUVR), which needs Aβ positron emission tomography (PET) normalization processing. There are two methods to collect the T1-weighted imaging (T1WI) for normalization: (i) anatomical standardization using simultaneously acquired T1WI (PET/MRI), usually adapted to PET images from PET/MRI scanners, and (ii) T1WI from a separate examination (PET + MRI), usually adapted to PET images from PET/CT scanners. This study aimed to elucidate the correlations and differences in CLs between when using the above two T1WI collection methods.

METHODS

Among patients who underwent Aβ PET/MRI (using 11C-Pittuberg compound B (11C-PiB) or 18F-flutemetamol (18F-FMM)) at our institution from 2015 to 2023, we selected 49 patients who also underwent other additional MRI examinations, including T1WI for anatomic standardization within 3 years. Thirty-one of them underwent 11C-PiB PET/MRI, and 18 participants underwent 18F-FMM PET/MRI. Twenty-five of them, additional MRI acquisition parameters were identical to simultaneous MRI during PET, and 24 participants were different. After normalization using PET/MRI or PET + MRI method each, SUVR was measured using the Global Alzheimer's Association Initiative Network cerebral cortical and striatum Volume of Interest templates (VOI) and whole cerebellum VOI. Subsequently, CLs were calculated using the previously established equations for each Aβ PET tracer.

RESULTS

Between PET/MRI and PET + MRI methods, CLs correlated linearly in 11C-PiB PET (y = 1.00x - 0.11, R2 = 0.999), 18F-FMM PET (y = 0.97x - 0.12, 0.997), identical additional MRI acquisition (y = 1.00x + 0.33, 0.999), different acquisition (y = 0.98x - 0.43, 0.997), and entire study group (y = 1.00x - 0.24, 0.999). Wilcoxon signed-rank test revealed no significant differences: 11C-PiB (p = 0.49), 18F-FMM (0.08), and whole PET (0.46). However, significant differences were identified in identical acquisition (p = 0.04) and different acquisition (p = 0.02). Bland-Altman analysis documented only a small bias between PET/MRI and PET + MRI in 11C-PiB PET, 18F-FMM PET, identical additional MRI acquisition, different acquisition, and whole PET (- 0.05, 0.67, - 0.30, 0.78, and 0.21, respectively).

CONCLUSIONS

Anatomical standardizations using PET/MRI and using PET + MRI can lead to almost equivalent CL. The CL values obtained using PET/MRI or PET + MRI normalization methods are consistent and comparable in clinical studies.

Comparison of consistency in centiloid scale among different analytical methods in amyloid PET: the CapAIBL, VIZCalc, and Amyquant methods

OBJECTIVE

The Centiloid (CL) scale is a standardized measure for quantifying amyloid deposition in amyloid positron emission tomography (PET) imaging. We aimed to assess the agreement among 3 CL calculation methods: CapAIBL, VIZCalc, and Amyquant.

METHODS

This study included 192 participants (mean age: 71.5 years, range: 50-87 years), comprising 55 with Alzheimer's disease, 65 with mild cognitive impairment, 13 with non-Alzheimer's dementia, and 59 cognitively normal participants. All the participants were assessed using the three CL calculation methods. Spearman's rank correlation, linear regression, Friedman tests, Wilcoxon signed-rank tests, and Bland-Altman analysis were employed to assess data correlations, linear associations, method differences, and systematic bias, respectively.

RESULTS

Strong correlations (rho = 0.99, p < .001) were observed among the CL values calculated using the three methods. Scatter plots and regression lines visually confirmed these strong correlations and met the validation criteria. Despite the robust correlations, a significant difference in CL value between CapAIBL and Amyquant was observed (36.1 ± 39.7 vs. 34.9 ± 39.4; p < .001). In contrast, no significant differences were found between CapAIBL and VIZCalc or between VIZCalc and Amyquant. The Bland-Altman analysis showed no observable systematic bias between the methods.

CONCLUSIONS

The study demonstrated strong agreement among the three methods for calculating CL values. Despite minor variations in the absolute values of the Centiloid scores obtained using these methods, the overall agreement suggests that they are interchangeable.

The Major Hypotheses of Alzheimer's Disease: Related Nanotechnology-Based Approaches for Its Diagnosis and Treatment

Alzheimer's disease (AD) is a well-known chronic neurodegenerative disorder that leads to the progressive death of brain cells, resulting in memory loss and the loss of other critical body functions. In March 2019, one of the major pharmaceutical companies and its partners announced that currently, there is no drug to cure AD, and all clinical trials of the new ones have been cancelled, leaving many people without hope. However, despite the clear message and startling reality, the research continued. Finally, in the last two years, the Food and Drug Administration (FDA) approved the first-ever medications to treat Alzheimer's, aducanumab and lecanemab. Despite researchers' support of this decision, there are serious concerns about their effectiveness and safety. The validation of aducanumab by the Centers for Medicare and Medicaid Services is still pending, and lecanemab was authorized without considering data from the phase III trials. Furthermore, numerous reports suggest that patients have died when undergoing extended treatment. While there is evidence that aducanumab and lecanemab may provide some relief to those suffering from AD, their impact remains a topic of ongoing research and debate within the medical community. The fact is that even though there are considerable efforts regarding pharmacological treatment, no definitive cure for AD has been found yet. Nevertheless, it is strongly believed that modern nanotechnology holds promising solutions and effective clinical strategies for the development of diagnostic tools and treatments for AD. This review summarizes the major hallmarks of AD, its etiological mechanisms, and challenges. It explores existing diagnostic and therapeutic methods and the potential of nanotechnology-based approaches for recognizing and monitoring patients at risk of irreversible neuronal degeneration. Overall, it provides a broad overview for those interested in the evolving areas of clinical neuroscience, AD, and related nanotechnology. With further research and development, nanotechnology-based approaches may offer new solutions and hope for millions of people affected by this devastating disease.

Blood-based biomarkers for Alzheimer's disease: Current state and future use in a transformed global healthcare landscape

Timely detection of the pathophysiological changes and cognitive impairment caused by Alzheimer's disease (AD) is increasingly pressing because of the advent of biomarker-guided targeted therapies that may be most effective when provided early in the disease. Currently, diagnosis and management of early AD are largely guided by clinical symptoms. FDA-approved neuroimaging and cerebrospinal fluid biomarkers can aid detection and diagnosis, but the clinical implementation of these testing modalities is limited because of availability, cost, and perceived invasiveness. Blood-based biomarkers (BBBMs) may enable earlier and faster diagnoses as well as aid in risk assessment, early detection, prognosis, and management. Herein, we review data on BBBMs that are closest to clinical implementation, particularly those based on measures of amyloid-β peptides and phosphorylated tau species. We discuss key parameters and considerations for the development and potential deployment of these BBBMs under different contexts of use and highlight challenges at the methodological, clinical, and regulatory levels.

Amyloid β-based therapy for Alzheimer's disease: challenges, successes and future

Amyloid β protein (Aβ) is the main component of neuritic plaques in Alzheimer's disease (AD), and its accumulation has been considered as the molecular driver of Alzheimer's pathogenesis and progression. Aβ has been the prime target for the development of AD therapy. However, the repeated failures of Aβ-targeted clinical trials have cast considerable doubt on the amyloid cascade hypothesis and whether the development of Alzheimer's drug has followed the correct course. However, the recent successes of Aβ targeted trials have assuaged those doubts. In this review, we discussed the evolution of the amyloid cascade hypothesis over the last 30 years and summarized its application in Alzheimer's diagnosis and modification. In particular, we extensively discussed the pitfalls, promises and important unanswered questions regarding the current anti-Aβ therapy, as well as strategies for further study and development of more feasible Aβ-targeted approaches in the optimization of AD prevention and treatment.

The Structural Combination of SIL and MODAG Scaffolds Fails to Enhance Binding to α-Synuclein but Reveals Promising Affinity to Amyloid β

A technique to image α-synuclein (αSYN) fibrils in vivo is an unmet scientific and clinical need that would represent a transformative tool in the understanding, diagnosis, and treatment of various neurodegenerative diseases. Several classes of compounds have shown promising results as potential PET tracers, but no candidate has yet exhibited the affinity and selectivity required to reach clinical application. We hypothesized that the application of the rational drug design technique of molecular hybridization to two promising lead scaffolds could enhance the binding to αSYN up to the fulfillment of those requirements. By combining the structures of SIL and MODAG tracers, we developed a library of diarylpyrazoles (DAPs). In vitro evaluation through competition assays against [³H]SIL26 and [³H]MODAG-001 showed the novel hybrid scaffold to have preferential binding affinity for amyloid β (Aβ) over αSYN fibrils. A ring-opening modification on the phenothiazine building block to produce analogs with increased three-dimensional flexibility did not result in an improved αSYN binding but a complete loss of competition, as well as a significant reduction in Aβ affinity. The combination of the phenothiazine and the 3,5-diphenylpyrazole scaffolds into DAP hybrids did not generate an enhanced αSYN PET tracer lead compound. Instead, these efforts identified a scaffold for promising Aβ ligands that may be relevant to the treatment and monitoring of Alzheimer's disease (AD).

Single-domain antibody-based noninvasive in vivo imaging of α-synuclein or tau pathology

Intracellular deposition of α-synuclein and tau are hallmarks of synucleinopathies and tauopathies, respectively. Recently, several dye-based imaging probes with selectivity for tau aggregates have been developed, but suitable imaging biomarkers for synucleinopathies are still unavailable. Detection of both of these aggregates early in the disease process may allow for prophylactic therapies before functional impairments have manifested, highlighting the importance of developing specific imaging probes for these lesions. In contrast to the β sheet dyes, single-domain antibodies, found in camelids and a few other species, are highly specific, and their small size allows better brain entry and distribution than whole antibodies. Here, we have developed such imaging ligands via phage display libraries derived from llamas immunized with α-synuclein and tau preparations, respectively. These probes allow noninvasive and specific in vivo imaging of α-synuclein versus tau pathology in mice, with the brain signal correlating strongly with lesion burden. These small antibody derivatives have great potential for in vivo diagnosis of these diseases.

The Roles of the Amyloid Beta Monomers in Physiological and Pathological Conditions

Amyloid beta peptide is an important biomarker in Alzheimer's disease, with the amyloidogenic hypothesis as one of the central hypotheses trying to explain this type of dementia. Despite numerous studies, the etiology of Alzheimer's disease remains incompletely known, as the pathological accumulation of amyloid beta aggregates cannot fully explain the complex clinical picture of the disease. Or, for the development of effective therapies, it is mandatory to understand the roles of amyloid beta at the brain level, from its initial monomeric stage prior to aggregation in the form of senile plaques. In this sense, this review aims to bring new, clinically relevant data on a subject intensely debated in the literature in the last years. In the first part, the amyloidogenic cascade is reviewed and the possible subtypes of amyloid beta are differentiated. In the second part, the roles played by the amyloid beta monomers in physiological and pathological (neurodegenerative) conditions are illustrated based on the most relevant and recent studies published on this topic. Finally, considering the importance of amyloid beta monomers in the pathophysiology of Alzheimer's disease, new research directions with diagnostic and therapeutic impacts are suggested.

Should artificial intelligence be used in conjunction with Neuroimaging in the diagnosis of Alzheimer's disease?

Alzheimer's disease (AD) is a progressive, neurodegenerative disorder that affects memory, thinking, behavior, and other cognitive functions. Although there is no cure, detecting AD early is important for the development of a therapeutic plan and a care plan that may preserve cognitive function and prevent irreversible damage. Neuroimaging, such as magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET), has served as a critical tool in establishing diagnostic indicators of AD during the preclinical stage. However, as neuroimaging technology quickly advances, there is a challenge in analyzing and interpreting vast amounts of brain imaging data. Given these limitations, there is great interest in using artificial Intelligence (AI) to assist in this process. AI introduces limitless possibilities in the future diagnosis of AD, yet there is still resistance from the healthcare community to incorporate AI in the clinical setting. The goal of this review is to answer the question of whether AI should be used in conjunction with neuroimaging in the diagnosis of AD. To answer the question, the possible benefits and disadvantages of AI are discussed. The main advantages of AI are its potential to improve diagnostic accuracy, improve the efficiency in analyzing radiographic data, reduce physician burnout, and advance precision medicine. The disadvantages include generalization and data shortage, lack of in vivo gold standard, skepticism in the medical community, potential for physician bias, and concerns over patient information, privacy, and safety. Although the challenges present fundamental concerns and must be addressed when the time comes, it would be unethical not to use AI if it can improve patient health and outcome.

Effect of reduction in brain amyloid levels on change in cognitive and functional decline in randomized clinical trials: An instrumental variable meta-analysis

INTRODUCTION

Whether the reduction in brain amyloid beta (Aβ) plaque alone may substantially slow cognitive and functional decline in patients with dementia or mild cognitive impairment due to Alzheimer's disease (AD) remains debated.

METHODS

An instrumental variable meta-analysis was performed to infer the effect of change in positron emission tomography (PET)-measured Aβ standardized uptake value ratio (SUVR) on cognitive and functional decline.

RESULTS

Pooling data from 16 randomized trials demonstrates that each 0.1-unit decrease in PET Aβ SUVR is associated with a reduction (95% confidence interval) by 0.09 (0.034-0.15), 0.33 (0.12-0.55), and 0.13 (0.017-0.24) point in the average change of the Clinical Dementia Rating-Sum of Boxes, the Alzheimer's Disease Assessment Scale-Cognitive Subscale, and the Mini-Mental State Examination, respectively.

DISCUSSION

This meta-analysis provides statistically significant evidence of a likely causal relationship between a reduction in Aβ plaque and a reduction in cognitive and functional decline in patients with AD.

HIGHLIGHTS

A widely cited meta-analysis article concluded amyloid beta reduction does not substantially improve cognition. We identified data inconsistencies in the initial publication and found new trial data. We repeated the meta-analysis after correcting data inconsistencies and adding new trial data. Updated results suggested statistically significant clinical benefit of amyloid beta reduction. Amyloid beta is a viable biological target for the treatment and prevention of AD.

Near-infrared fluorescence lifetime imaging of amyloid-β aggregates and tau fibrils through the intact skull of mice

Non-invasive methods for the in vivo detection of hallmarks of Alzheimer's disease can facilitate the study of the progression of the disease in mouse models and may enable its earlier diagnosis in humans. Here we show that the zwitterionic heptamethine fluorophore ZW800-1C, which has peak excitation and emission wavelengths in the near-infrared optical window, binds in vivo and at high contrast to amyloid-β deposits and to neurofibrillary tangles, and allows for the microscopic imaging of amyloid-β and tau aggregates through the intact skull of mice. In transgenic mouse models of Alzheimer's disease, we compare the performance of ZW800-1C with that of the two spectrally similar heptamethine fluorophores ZW800-1A and indocyanine green, and show that ZW800-1C undergoes a longer fluorescence-lifetime shift when bound to amyloid-β and tau aggregates than when circulating in blood vessels. ZW800-1C may prove advantageous for tracking the proteinic aggregates in rodent models of amyloid-β and tau pathologies.

Brain PET Imaging: Frontotemporal Dementia

Brain PET adds value in diagnosing neurodegenerative disorders, especially frontotemporal dementia (FTD) due to its syndromic presentation that overlaps with a variety of other neurodegenerative and psychiatric disorders. 18F-FDG-PET has improved sensitivity and specificity compared with structural MR imaging, with optimal diagnostic results achieved when both techniques are utilized. PET demonstrates superior sensitivity compared with SPECT for FTD diagnosis that is primarily a supplement to other imaging and clinical evaluations. Tau-PET and amyloid-PET primary use in FTD diagnosis is differentiation from Alzheimer disease, although these methods are limited mainly to research settings.

Decreased Hemodynamic Responses in Left Parietal Lobule and Left Inferior Parietal Lobule in Older Adults with Mild Cognitive Impairment: A Near-Infrared Spectroscopy Study

Background: The brain activation patterns of mild cognitive impairment (MCI) are still unclear and they involve multiple brain regions. Most previous studies have focused on abnormal activation in the frontal and temporal lobes, with few investigating the entire brain. Objective: To identify and compare the changes in cerebral hemodynamics and abnormal activation patterns in the entire brain of MCI patients and healthy older adults. Methods: Patients with MCI (n = 22) and healthy controls (HC, n = 34) matched by age, education levels, sex, and mental state were enrolled. They performed the same letter and category verbal fluency test (VFT) tasks while their behavioral performance and global cerebral hemodynamics were analyzed. Results: The performance during the category VFT task was significantly better than that during the letter VFT task across all participants (HC: correct: p <  0.001; intrusions: p <  0.001; MCI: correct: p <  0.001; intrusions: p <  0.001). The number of correct words during the letter and category VFT tasks was significantly higher in the HC group than in the MCI group (p <  0.001). The deoxygenated-hemoglobin (HbR) concentrations in the left parietal lobule (p = 0.0352) and left inferior parietal lobule (p = 0.0314) were significantly different during the category VFT task. Conclusion: The differences between HC and MCI groups were greater in the category task. The HbR concentration was more sensitive for the category VFT task and concentration changes in the left parietal lobule and left inferior parietal lobule may be useful for clinical screening and application; thus, they deserve more attention.

Diagnostic performance of automated plasma amyloid-β assays combined with pre-analytical immunoprecipitation

Background

Measurements of the amyloid-β (Aβ) 42/40 ratio in blood plasma may support the early diagnosis of Alzheimer’s disease and aid in the selection of suitable participants in clinical trials. Here, we compared the diagnostic performance of fully automated prototype plasma Aβ42/40 assays with and without pre-analytical sample workup by immunoprecipitation.

Methods

A pre-selected clinical sample comprising 42 subjects with normal and 38 subjects with low cerebrospinal fluid (CSF) Aβ42/40 ratios was studied. The plasma Aβ42/40 ratios were determined with fully automated prototype Elecsys® immunoassays (Roche Diagnostics GmbH, Penzberg, Germany) by direct measurements in EDTA plasma or after pre-analytical Aβ immunoprecipitation. The diagnostic performance for the detection of abnormal CSF Aβ42/40 was analyzed by receiver operating characteristic (ROC) analysis. In an additional post hoc analysis, a biomarker-supported clinical diagnosis was used as a second endpoint.

Results

Pre-analytical immunoprecipitation resulted in a significant increase in the area under the ROC curve (AUC) from 0.73 to 0.88 (p = 0.01547) for identifying subjects with abnormal CSF Aβ42/40. A similar improvement in the diagnostic performance by pre-analytical immunoprecipitation was also observed when a biomarker-supported clinical diagnosis was used as a second endpoint (AUC increase from 0.77 to 0.92, p = 0.01576).

Conclusions

Our preliminary observations indicate that pre-analytical Aβ immunoprecipitation can improve the diagnostic performance of plasma Aβ assays for detecting brain amyloid pathology. The findings may aid in the further development of blood-based immunoassays for Alzheimer’s disease ultimately suitable for screening and routine use.

Quantification of amyloid PET for future clinical use: a state-of-the-art review

Amyloid-β (Aβ) pathology is one of the earliest detectable brain changes in Alzheimer's disease (AD) pathogenesis. The overall load and spatial distribution of brain Aβ can be determined in vivo using positron emission tomography (PET), for which three fluorine-18 labelled radiotracers have been approved for clinical use. In clinical practice, trained readers will categorise scans as either Aβ positive or negative, based on visual inspection. Diagnostic decisions are often based on these reads and patient selection for clinical trials is increasingly guided by amyloid status. However, tracer deposition in the grey matter as a function of amyloid load is an inherently continuous process, which is not sufficiently appreciated through binary cut-offs alone. State-of-the-art methods for amyloid PET quantification can generate tracer-independent measures of Aβ burden. Recent research has shown the ability of these quantitative measures to highlight pathological changes at the earliest stages of the AD continuum and generate more sensitive thresholds, as well as improving diagnostic confidence around established binary cut-offs. With the recent FDA approval of aducanumab and more candidate drugs on the horizon, early identification of amyloid burden using quantitative measures is critical for enrolling appropriate subjects to help establish the optimal window for therapeutic intervention and secondary prevention. In addition, quantitative amyloid measurements are used for treatment response monitoring in clinical trials. In clinical settings, large multi-centre studies have shown that amyloid PET results change both diagnosis and patient management and that quantification can accurately predict rates of cognitive decline. Whether these changes in management reflect an improvement in clinical outcomes is yet to be determined and further validation work is required to establish the utility of quantification for supporting treatment endpoint decisions. In this state-of-the-art review, several tools and measures available for amyloid PET quantification are summarised and discussed. Use of these methods is growing both clinically and in the research domain. Concurrently, there is a duty of care to the wider dementia community to increase visibility and understanding of these methods.

Patterns of Distribution of 18F-THK5351 Positron Emission Tomography in Alzheimer's Disease Continuum

BACKGROUND

Alzheimer's disease (AD) is conceptualized as a biological continuum encompassing the preclinical (clinically asymptomatic but with evidence of AD pathology) and clinical (symptomatic) phases.

OBJECTIVE

Using 18F-THK5351 as a tracer that binds to both tau and MAO-B, we investigated the changes in 18F-THK5351 accumulation patterns in AD continuum individuals with positive amyloid PET consisting of cognitively normal individuals (CNp), amnestic mild cognitive impairment (aMCI), and AD and cognitively normal individuals (CNn) with negative amyloid PET.

METHODS

We studied 69 individuals (32 CNn, 11 CNp, 9 aMCI, and 17 AD) with structural magnetic resonance imaging, 11C-Pittsburgh compound-B (PIB) and 18F-THK5351 PET, and neuropsychological assessment. 18F-THK5351 accumulation was evaluated with visual analysis, voxel-based analysis and combined region of interest (ROI)-based analysis corresponding to Braak neurofibrillary tangle stage.

RESULTS

On visual analysis, 18F-THK5351 accumulation was increased with stage progression in the AD continuum. On voxel-based analysis, there was no statistical difference in 18F-THK5351 accumulation between CNp and CNn. However, a slight increase of the bilateral posterior cingulate gyrus in aMCI and definite increase of the bilateral parietal temporal association area and posterior cingulate gyrus/precuneus in AD were detected compared with CNn. On ROI-based analyses, 18F-THK5351 accumulation correlated positively with supratentorial 11C-PIB accumulation and negatively with the hippocampal volume and neuropsychological assessment.

CONCLUSION

The AD continuum showed an increase in 18F-THK5351 with stage progression, suggesting that 18F-THK5351 has the potential to visualize the severity of tau deposition and neurodegeneration in accordance with the AD continuum.

Blood-based high sensitivity measurements of beta-amyloid and phosphorylated tau as biomarkers of Alzheimer's disease: a focused review on recent advances

Discovery and development of clinically useful biomarkers for Alzheimer's disease (AD) and related dementias have been the focus of recent research efforts. While cerebrospinal fluid and positron emission tomography or MRI-based neuroimaging markers have made the in vivo detection of AD pathology and its consequences possible, the high cost and invasiveness have limited their widespread use in the clinical setting. On the other hand, advances in potentially more accessible blood-based biomarkers had been impeded by lack of sensitivity in detecting changes in markers of the hallmarks of AD, including amyloid-β (Aβ) peptides and phosphorylated tau (P-tau). More recently, however, emerging technologies with superior sensitivity and specificity for measuring Aβ and P-tau have reported high concordances with AD severity. In this focused review, we describe several emerging technologies, including immunoprecipitation-mass spectrometry (IP-MS), single molecule array and Meso Scale Discovery immunoassay platforms, and appraise the current literature arising from their use to identify plaques, tangles and other AD-associated pathology. While there is potential clinical utility in adopting these technologies, we also highlight the further studies needed to establish Aβ and P-tau as blood-based biomarkers for AD, including validation with existing large sample sets, new independent cohorts from diverse backgrounds as well as population-based longitudinal studies. In conclusion, the availability of sensitive and reliable measurements of Aβ peptides and P-tau species in blood holds promise for the diagnosis, prognosis and outcome assessments in clinical trials for AD.

Improvement of electroacupuncture on APP/PS1 transgenic mice in behavioral probably due to reducing deposition of Aβ in hippocampus

Alzheimer's disease (AD) is a fatal neurodegenerative disease for which currently no cure is available. Electroacupuncture (EA) has been widely used in China as an alternative therapeutic approach for neurological diseases. The cognitive decline in patients with AD has been reported to be closely related to the deposition of amyloid-β (Aβ) in the hippocampus of the brain, and the Morris water maze (MWM) test is a widely used method for assessing the behavior of animal models. In this study, the MWM test was performed to evaluate the effects of EA treatment on cognitive function and memory, and the micro-positron emission tomography scan was used to assess the hippocampal Aβ deposition. The results showed that the cognitive function of APP/PS1 mice was significantly improved and the rate of [18F]AV-45 uptake was reduced in the EA group, compared with the AD group. Our study suggested that EA can exert a therapeutic effect in AD by improving spatial learning and memory and inhibiting the hippocampal Aβ deposition.

Emerging topics in dementia care and services

BACKGROUND

The National Institute on Aging (NIA), in conjunction with the Department of Health and Human Services as part of the National Alzheimer's Project Act (NAPA), convened a 2020 Dementia Care, Caregiving, and Services Research Summit Virtual Meeting Series. This review article summarizes three areas of emerging science that are likely to grow in importance given advances in measurement, technologies, and diagnostic tests that were presented at the Summit.

RESULTS

Dr. Cassel discussed novel ethical considerations that have resulted from scientific advances that have enabled early diagnosis of pre-clinical dementia. Dr. Monin then summarized issues regarding emotional experiences in persons with dementia and their caregivers and care partners, including the protective impact of positive emotion and heterogeneity of differences in emotion by dementia type and individual characteristics that affect emotional processes with disease progression. Finally, Dr. Jared Benge provided an overview of the role of technologies in buffering the impact of cognitive change on real-world functioning and their utility in safety and monitoring of function and treatment adherence, facilitating communication and transportation, and increasing access to specialists in underserved or remote areas.

CONCLUSIONS

National policy initiatives, supported by strong advocacy and increased federal investments, have accelerated the pace of scientific inquiry and innovation related to dementia care and services but have raised some new concerns regarding ethics, disparities, and attending to individual needs, capabilities, and preferences.

Fluorine-19 Magnetic Resonance Imaging for Detection of Amyloid β Oligomers Using a Keto Form of Curcumin Derivative in a Mouse Model of Alzheimer's Disease

Recent evidence suggests that the formation of soluble amyloid β (Aβ) aggregates with high toxicity, such as oligomers and protofibrils, is a key event that causes Alzheimer's disease (AD). However, understanding the pathophysiological role of such soluble Aβ aggregates in the brain in vivo could be difficult due to the lack of a clinically available method to detect, visualize, and quantify soluble Aβ aggregates in the brain. We had synthesized a novel fluorinated curcumin derivative with a fixed keto form, named as Shiga-Y51, which exhibited high selectivity to Aβ oligomers in vitro. In this study, we investigated the in vivo detection of Aβ oligomers by fluorine-19 (¹⁹F) magnetic resonance imaging (MRI) using Shiga-Y51 in an APP/PS1 double transgenic mouse model of AD. Significantly high levels of ¹⁹F signals were detected in the upper forebrain region of APP/PS1 mice compared with wild-type mice. Moreover, the highest levels of Aβ oligomers were detected in the upper forebrain region of APP/PS1 mice in enzyme-linked immunosorbent assay. These findings suggested that ¹⁹F-MRI using Shiga-Y51 detected Aβ oligomers in the in vivo brain. Therefore, ¹⁹F-MRI using Shiga-Y51 with a 7 T MR scanner could be a powerful tool for imaging Aβ oligomers in the brain.